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4 vulnerabilities by libass
CVE-2026-61627 (GCVE-0-2026-61627)
Vulnerability from nvd – Published: 2026-10-30 14:55 – Updated: 2026-10-30 15:51
VLAI
EPSS
VEX
Title
libass: Out-of-bounds read and write in wrap_lines_measure
Summary
libass is a portable subtitle renderer for the `ASS`/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. Prior to 0.17.5, libass can overread and overwrite the glyph array in `wrap_lines_measure` while rendering malicious `ASS` content. In `wrap modes other than two`, a final line ending with a literal backslash-n sequence and otherwise consisting only of such sequences or spaces can remain after early trimming and make the line-measurement loops overshoot by one glyph. When the total text size exactly matches the allocated glyph-array capacity, the first loop reads an uninitialized 32-bit fixed-point `pos.x` value, although that value is not subsequently used. The second loop writes `pos.x` and `pos.y` beyond the array, zeroing the first and adding an attacker-controllable offset to the second. No actual exploitation beyond possible denial of service is known; broader exploitation is theoretical and constrained by the addresses, limited writes, and ASLR. This issue is fixed in version 0.17.5.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-30 15:34 UTC
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/libass/libass/security/advisor… | x_refsource_CONFIRM |
| https://github.com/libass/libass/commit/f2ef59755… | x_refsource_MISC |
| https://github.com/libass/libass/releases/tag/0.17.5 | x_refsource_MISC |
| https://lists.debian.org/debian-lts-announce/2026… |
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"discovery": "UNKNOWN"
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CVE-2026-61626 (GCVE-0-2026-61626)
Vulnerability from nvd – Published: 2026-10-30 14:52 – Updated: 2026-10-30 14:52
VLAI
EPSS
VEX
Title
libass: Out-of-bounds bit clears for negative Matroska ReadOrder values
Summary
libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. From 0.17.4 until 0.17.5, libass event pruning does not guard negative Matroska `ReadOrder` values, allowing an attacker to clear arbitrarily many bits to zero at attacker-controlled positions near the NULL pointer. Exploitation requires a malicious Matroska stream loaded through `ass_process_chunk`, enabled read-order checking, and later pruning of the malicious events. Read-order checking is enabled by default unless `ass_set_check_readorder` is called with zero; pruning must occur explicitly through `ass_prune_events` or through automatic pruning previously enabled with `ass_configure_prune`. On common systems with arithmetic right shift, 32-bit int values, the upper address region reserved to the kernel, and matching binary/kernel architecture, the expected consequence is denial of service. More extensive exploitation on uncommon systems is theoretical and strongly constrained by the target addresses, bit-clearing-only mutation, and ASLR. This issue is fixed in version 0.17.5.
Severity
CWE
- CWE-787 - Out-of-bounds Write
Assigner
References
3 references
| URL | Tags |
|---|---|
| https://github.com/libass/libass/security/advisor… | x_refsource_CONFIRM |
| https://github.com/libass/libass/commit/23da65a13… | x_refsource_MISC |
| https://github.com/libass/libass/releases/tag/0.17.5 | x_refsource_MISC |
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CVE-2026-61627 (GCVE-0-2026-61627)
Vulnerability from cvelistv5 – Published: 2026-10-30 14:55 – Updated: 2026-10-30 15:51
VLAI
EPSS
VEX
Title
libass: Out-of-bounds read and write in wrap_lines_measure
Summary
libass is a portable subtitle renderer for the `ASS`/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. Prior to 0.17.5, libass can overread and overwrite the glyph array in `wrap_lines_measure` while rendering malicious `ASS` content. In `wrap modes other than two`, a final line ending with a literal backslash-n sequence and otherwise consisting only of such sequences or spaces can remain after early trimming and make the line-measurement loops overshoot by one glyph. When the total text size exactly matches the allocated glyph-array capacity, the first loop reads an uninitialized 32-bit fixed-point `pos.x` value, although that value is not subsequently used. The second loop writes `pos.x` and `pos.y` beyond the array, zeroing the first and adding an attacker-controllable offset to the second. No actual exploitation beyond possible denial of service is known; broader exploitation is theoretical and constrained by the addresses, limited writes, and ASLR. This issue is fixed in version 0.17.5.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-30 15:34 UTC
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/libass/libass/security/advisor… | x_refsource_CONFIRM |
| https://github.com/libass/libass/commit/f2ef59755… | x_refsource_MISC |
| https://github.com/libass/libass/releases/tag/0.17.5 | x_refsource_MISC |
| https://lists.debian.org/debian-lts-announce/2026… |
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CVE-2026-61626 (GCVE-0-2026-61626)
Vulnerability from cvelistv5 – Published: 2026-10-30 14:52 – Updated: 2026-10-30 14:52
VLAI
EPSS
VEX
Title
libass: Out-of-bounds bit clears for negative Matroska ReadOrder values
Summary
libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. From 0.17.4 until 0.17.5, libass event pruning does not guard negative Matroska `ReadOrder` values, allowing an attacker to clear arbitrarily many bits to zero at attacker-controlled positions near the NULL pointer. Exploitation requires a malicious Matroska stream loaded through `ass_process_chunk`, enabled read-order checking, and later pruning of the malicious events. Read-order checking is enabled by default unless `ass_set_check_readorder` is called with zero; pruning must occur explicitly through `ass_prune_events` or through automatic pruning previously enabled with `ass_configure_prune`. On common systems with arithmetic right shift, 32-bit int values, the upper address region reserved to the kernel, and matching binary/kernel architecture, the expected consequence is denial of service. More extensive exploitation on uncommon systems is theoretical and strongly constrained by the target addresses, bit-clearing-only mutation, and ASLR. This issue is fixed in version 0.17.5.
Severity
CWE
- CWE-787 - Out-of-bounds Write
Assigner
References
3 references
| URL | Tags |
|---|---|
| https://github.com/libass/libass/security/advisor… | x_refsource_CONFIRM |
| https://github.com/libass/libass/commit/23da65a13… | x_refsource_MISC |
| https://github.com/libass/libass/releases/tag/0.17.5 | x_refsource_MISC |
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}
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},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-61626",
"datePublished": "2026-10-30T14:52:21.006Z",
"dateReserved": "2026-07-10T17:38:57.110Z",
"dateUpdated": "2026-10-30T14:52:21.006Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}