CVE-2026-55951 (GCVE-0-2026-55951)
Vulnerability from cvelistv5 – Published: 2026-09-01 14:37 – Updated: 2026-11-11 13:56
VLAI
EPSS
VEX
Title
httpc memory exhaustion via unbounded response header accumulation
Summary
The Erlang/OTP httpc HTTP client does not enforce a limit on the total size of response headers received from a server. The max_header_size option defaults to nolimit, and httpc_response:parse_headers/6 accumulates every header into a list before the length check runs (which only fires after the terminating CRLF CRLF is received).
A malicious or compromised HTTP server can send an arbitrarily large number of headers, or headers with very large values, causing the client process to allocate unbounded memory until the system runs out of memory or the BEAM VM crashes. A proof-of-concept server sending 100,000 headers of roughly 4000 bytes each caused the client VM to allocate over 13 GB of memory in under 30 seconds.
Any application using httpc:request/4,5 to connect to untrusted servers is affected. No authentication is required: any server the client connects to (including via a redirect or man-in-the-middle) can trigger the exhaustion.
This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, OTP 28.5.0.6, and OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, 9.6.2.3, and 9.7.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-01 15:53 UTC
CWE
- CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
6 references
| URL | Tags |
|---|---|
| https://github.com/erlang/otp/security/advisories… | vendor-advisory |
| https://cna.erlef.org/cves/CVE-2026-55951.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-55951 | related |
| https://www.erlang.org/doc/system/versions.html#o… | x_version-scheme |
| https://github.com/erlang/otp/commit/aba0fe8c2d70… | patch |
| https://github.com/erlang/otp/commit/e3be1cfe9f6c… | patch |
Impacted products
3 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Erlang | OTP |
Affected:
17.0 , < *
(otp)
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:* |
||
| Erlang | OTP |
Affected:
5.10 , < *
(otp)
cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:* |
||
| Erlang | OTP |
Affected:
84adefa331c4159d432d22840663c38f155cd4c1 , < *
(git)
Unaffected: aba0fe8c2d700bf4ac94607cf7f00e53bbe4042d , < * (git) Unaffected: e3be1cfe9f6cedd0cd20d9905e05601dfb31c8aa , < * (git) cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:* |
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"modifiedAttackVector": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
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"vulnAvailabilityImpact": "HIGH",
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},
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
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"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/erlang/otp/commit/aba0fe8c2d700bf4ac94607cf7f00e53bbe4042d"
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{
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"url": "https://github.com/erlang/otp/security/advisories/GHSA-f9fw-mg7q-4g3x"
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{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
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{
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"sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
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"type": "Secondary"
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"vulnrichment": {
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"title": "CISA ADP Vulnrichment"
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{
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],
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}
],
"credits": [
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"lang": "en",
"type": "remediation developer",
"value": "Konrad Pietrzak / Ericsson"
}
],
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"lang": "en",
"supportingMedia": [
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"base64": false,
"type": "text/html",
"value": "\u003cp\u003eThe Erlang/OTP \u003ccode\u003ehttpc\u003c/code\u003e HTTP client does not enforce a limit on the total size of response headers received from a server. The \u003ccode\u003emax_header_size\u003c/code\u003e option defaults to \u003ccode\u003enolimit\u003c/code\u003e, and \u003ccode\u003ehttpc_response:parse_headers/6\u003c/code\u003e accumulates every header into a list before the length check runs (which only fires after the terminating CRLF CRLF is received).\u003c/p\u003e\n\u003cp\u003eA malicious or compromised HTTP server can send an arbitrarily large number of headers, or headers with very large values, causing the client process to allocate unbounded memory until the system runs out of memory or the BEAM VM crashes. A proof-of-concept server sending 100,000 headers of roughly 4000 bytes each caused the client VM to allocate over 13 GB of memory in under 30 seconds.\u003c/p\u003e\n\u003cp\u003eAny application using \u003ccode\u003ehttpc:request/4,5\u003c/code\u003e to connect to untrusted servers is affected. No authentication is required: any server the client connects to (including via a redirect or man-in-the-middle) can trigger the exhaustion.\u003c/p\u003e\n\u003cp\u003eThis issue affects OTP from OTP\u0026nbsp;17.0 before OTP\u0026nbsp;27.3.4.17, OTP\u0026nbsp;28.5.0.6, and OTP\u0026nbsp;29.0.6, corresponding to inets from 5.10 before 9.3.2.7, 9.6.2.3, and 9.7.2. Whether OTP before OTP\u0026nbsp;17.0, corresponding to inets before 5.10, is affected is unknown.\u003c/p\u003e"
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"base64": false,
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"value": "The Erlang/OTP `httpc` HTTP client does not enforce a limit on the total size of response headers received from a server. The `max_header_size` option defaults to `nolimit`, and `httpc_response:parse_headers/6` accumulates every header into a list before the length check runs (which only fires after the terminating CRLF CRLF is received).\n\nA malicious or compromised HTTP server can send an arbitrarily large number of headers, or headers with very large values, causing the client process to allocate unbounded memory until the system runs out of memory or the BEAM VM crashes. A proof-of-concept server sending 100,000 headers of roughly 4000 bytes each caused the client VM to allocate over 13 GB of memory in under 30 seconds.\n\nAny application using `httpc:request/4,5` to connect to untrusted servers is affected. No authentication is required: any server the client connects to (including via a redirect or man-in-the-middle) can trigger the exhaustion.\n\nThis issue affects OTP from OTP\u00a017.0 before OTP\u00a027.3.4.17, OTP\u00a028.5.0.6, and OTP\u00a029.0.6, corresponding to inets from 5.10 before 9.3.2.7, 9.6.2.3, and 9.7.2. Whether OTP before OTP\u00a017.0, corresponding to inets before 5.10, is affected is unknown."
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}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.