libpng: Heap-based Buffer Overflow
CVE-2026-25646 is a high-severity heap-based buffer overflow vulnerability in libpng from Pnggroup, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected libpng versions: < 1.6.55. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.12% chance of exploitation within 30 days, higher than 67% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of libpng you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
Version data comes from the organisation that assigned the CVE; 12 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.3 | High | CNA (github.com) |
| CVSS 3.1 | 8.1 | High | NVD |
| CVSS 3.1 | 7.0 | High | CNA |
Official description
LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. Prior to 1.6.55, an out-of-bounds read vulnerability exists in the png_set_quantize() API function. When the function is called with no histogram and the number of colors in the palette is more than twice the maximum supported by the user's display, certain palettes will cause the function to enter into an infinite loop that reads past the end of an internal heap-allocated buffer. The images that trigger this vulnerability are valid per the PNG specification. This vulnerability is fixed in 1.6.55.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Heap-based Buffer Overflow
The product writes past the end of a buffer that was allocated on the heap.
How developers prevent this class of flaw
- Pre-design: Use a language or compiler that performs automatic bounds checking.
- Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
Other references
- openwall.com/lists/oss-security/2026/02/09/7Mailing List
- access.redhat.com/errata/RHSA-2026:10097
- access.redhat.com/errata/RHSA-2026:12274
- access.redhat.com/errata/RHSA-2026:14773
- access.redhat.com/errata/RHSA-2026:15087
- access.redhat.com/errata/RHSA-2026:16174
- access.redhat.com/errata/RHSA-2026:17596
- access.redhat.com/errata/RHSA-2026:3031
- access.redhat.com/errata/RHSA-2026:3405
- access.redhat.com/errata/RHSA-2026:3551
- access.redhat.com/errata/RHSA-2026:3573
- access.redhat.com/errata/RHSA-2026:3574
- access.redhat.com/errata/RHSA-2026:3575
- access.redhat.com/errata/RHSA-2026:3576
- access.redhat.com/errata/RHSA-2026:3577
Other vulnerabilities in libpng
- 7.6 High severity
- 7.5 High severity
- 7.8 High severity
- 7.1 High severity
- 7.1 High severity
- 7.1 High severity
Recent Heap-based Buffer Overflow vulnerabilities
- 7.3 High severity
- 7.5 High severity
- 9.1 Critical severity
- 8.0 High severity
- 8.0 High severity
- 8.0 High severity
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