CVE-2026-23191 (GCVE-0-2026-23191)

Vulnerability from cvelistv5 – Published: 2026-02-14 16:27 – Updated: 2026-09-14 11:58
VLAI
Title
ALSA: aloop: Fix racy access at PCM trigger
Summary
In the Linux kernel, the following vulnerability has been resolved: ALSA: aloop: Fix racy access at PCM trigger The PCM trigger callback of aloop driver tries to check the PCM state and stop the stream of the tied substream in the corresponding cable. Since both check and stop operations are performed outside the cable lock, this may result in UAF when a program attempts to trigger frequently while opening/closing the tied stream, as spotted by fuzzers. For addressing the UAF, this patch changes two things: - It covers the most of code in loopback_check_format() with cable->lock spinlock, and add the proper NULL checks. This avoids already some racy accesses. - In addition, now we try to check the state of the capture PCM stream that may be stopped in this function, which was the major pain point leading to UAF.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-16 20:20 UTC
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b1c73fc8e697eb73e23603e465e9af2711ed4183 , < f57467114f40c5aacebbea96fb4ff9e5cd2b7f18 (git)
Affected: b1c73fc8e697eb73e23603e465e9af2711ed4183 , < c99be0d5af02adebe9cb6f9869d20397fa9935a3 (git)
Affected: b1c73fc8e697eb73e23603e465e9af2711ed4183 , < f3ce8be893726899e3053cf8059ecc95d8410359 (git)
Affected: b1c73fc8e697eb73e23603e465e9af2711ed4183 , < 0e6245b2424d126ac90018142d09f0707e12998b (git)
Affected: b1c73fc8e697eb73e23603e465e9af2711ed4183 , < bad15420050db1803767e58756114800cce91ea4 (git)
Affected: b1c73fc8e697eb73e23603e465e9af2711ed4183 , < 5727ccf9d19ca414cb76d9b647883822e2789c2e (git)
Affected: b1c73fc8e697eb73e23603e465e9af2711ed4183 , < 826af7fa62e347464b1b4e0ba2fe19a92438084f (git)
guessed Create a notification for this product.
Linux Linux Affected: 2.6.37
Unaffected: 0 , < 2.6.37 (semver)
Unaffected: 5.10.270 , ≤ 5.10.* (semver)
Unaffected: 5.15.221 , ≤ 5.15.* (semver)
Unaffected: 6.1.188 , ≤ 6.1.* (semver)
Unaffected: 6.6.157 , ≤ 6.6.* (semver)
Unaffected: 6.12.70 , ≤ 6.12.* (semver)
Unaffected: 6.18.10 , ≤ 6.18.* (semver)
Unaffected: 6.19 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: aloop: Fix racy access at PCM trigger\n\nThe PCM trigger callback of aloop driver tries to check the PCM state\nand stop the stream of the tied substream in the corresponding cable.\nSince both check and stop operations are performed outside the cable\nlock, this may result in UAF when a program attempts to trigger\nfrequently while opening/closing the tied stream, as spotted by\nfuzzers.\n\nFor addressing the UAF, this patch changes two things:\n- It covers the most of code in loopback_check_format() with\n  cable-\u003elock spinlock, and add the proper NULL checks.  This avoids\n  already some racy accesses.\n- In addition, now we try to check the state of the capture PCM stream\n  that may be stopped in this function, which was the major pain point\n  leading to UAF."
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            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nALSA: aloop: Corrige el acceso con condiciones de carrera en el disparador PCM\n\nLa funci\u00f3n de devoluci\u00f3n de llamada del disparador PCM del controlador aloop intenta verificar el estado de PCM y detener el flujo del subflujo vinculado en el cable correspondiente. Dado que tanto las operaciones de verificaci\u00f3n como las de detenci\u00f3n se realizan fuera del bloqueo del cable, esto puede resultar en UAF cuando un programa intenta disparar frecuentemente mientras abre/cierra el flujo vinculado, como detectaron los fuzzers.\n\nPara abordar el UAF, este parche cambia dos cosas:\n- Cubre la mayor parte del c\u00f3digo en loopback_check_format() con el spinlock cable-\u0026gt;lock, y a\u00f1ade las comprobaciones de NULL adecuadas. Esto ya evita algunos accesos con condiciones de carrera.\n- Adem\u00e1s, ahora intentamos verificar el estado del flujo PCM de captura que puede ser detenido en esta funci\u00f3n, lo cual era el principal punto problem\u00e1tico que conduc\u00eda al UAF."
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        "id": "CVE-2026-23191",
        "lastModified": "2026-09-14T12:17:39.100",
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        "vulnStatus": "Modified",
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                "value": "CWE-416"
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            "source": "nvd@nist.gov",
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      "current_release_date": "2026-07-01T14:06:06+00:00",
      "cve": "CVE-2026-23191",
      "id": "CVE-2026-23191",
      "initial_release_date": "2026-02-14T00:00:00+00:00",
      "product_status:fixed": "2084",
      "product_status:known_affected": "22",
      "product_status:known_not_affected": "14",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ALSA: aloop: Fix racy access at PCM trigger",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23191.json",
      "version": "3"
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    "vulnrichment": {
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              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
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                  "version": "6.19",
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                  "value": "AV:L - The vulnerability is in the ALSA aloop PCM driver, accessed through local sound device files (/dev/snd/pcmC*D*p and /dev/snd/pcmC*D*c). No network or adjacent access path exists.\nAC:L - The attacker fully controls both sides of the race condition \u2014 they can concurrently trigger PCM start on one substream while closing the paired substream. The race is reliably winnable by the attacker, as confirmed by syzbot reproducibility.\nPR:L - Accessing ALSA PCM device files requires a local unprivileged user with audio group membership or equivalent permissions, which is standard on desktop Linux and Android. The snd-aloop module must be loaded, but no root/admin privileges are required to trigger the bug once available.\nUI:N - No user interaction is required. The attacker can open, trigger, and close PCM substreams entirely on their own.\nS:U - The vulnerability and its impact remain within the kernel\u0027s security authority. There is no crossing of a security boundary such as a VM escape or sandbox escape.\nC:H - This is a use-after-free vulnerability where freed loopback_pcm and runtime structures are dereferenced. An attacker can reclaim the freed memory with controlled data, enabling arbitrary kernel memory reads.\nI:H - The UAF allows the attacker to reclaim freed heap objects via heap spraying, providing arbitrary write primitives and potential control flow hijacking through corrupted function pointers in the loopback_pcm or runtime structures.\nA:H - The use-after-free reliably causes kernel crashes (oops/panic) when the freed memory is accessed, as demonstrated by the syzbot fuzzer report."
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}



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Taxonomy of the tags.





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.


Detection rules are retrieved from Rulezet.


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.