Raw vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:HSummary
CVE-2026-33416 is a high-severity Use After Free (CWE-416) vulnerability in Libpng Libpng. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked in the top 39% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-33416 is a use-after-free vulnerability (CWE-416) in the LIBPNG library, a reference implementation for reading, creating, and manipulating PNG raster image files. The issue affects versions 1.2.1 through 1.6.55 and stems from the `png_set_tRNS` and `png_set_PLTE` functions, which alias heap-allocated buffers between `png_struct` and `png_info` structures that have independent lifetimes. Specifically, `png_set_tRNS` shares a 256-byte `trans_alpha` buffer, and `png_set_PLTE` shares a 768-byte `palette` buffer. Calling `png_free_data` with `PNG_FREE_TRNS` or `PNG_FREE_PLTE` frees the buffer via `info_ptr`, leaving a dangling pointer in `png_ptr`. Subsequent row-transform functions then dereference and potentially write to the freed memory. A second call to either function triggers the same issue, as they internally invoke `png_free_data` before reallocating.
Remote attackers can exploit this vulnerability over a network with no privileges required, though it demands high attack complexity and user interaction, such as convincing a user to process a malicious PNG file in an affected application. Successful exploitation leads to high-impact consequences, including arbitrary code execution, data disclosure, or denial of service, as indicated by the CVSS v3.1 base score of 7.5 (AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H). Applications embedding LIBPNG for PNG handling are at risk if they invoke these functions in the described sequence.
The vulnerability is fixed in LIBPNG version 1.6.56. Mitigation involves upgrading to this patched release, with relevant changes detailed in upstream GitHub commits such as 23019269764e35ed8458e517f1897bd3c54820eb, 7ea9eea884a2328cc7fdcb3c0c00246a50d90667, a3a21443ed12bfa1ef46fa0d4fb2b74a0fa34a25, and c1b0318b393c90679e6fa5bc1d329fd5d5012ec1, as well as pull request 824. Security practitioners should audit dependent libraries in software stacks and apply patches promptly.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-16258
Vulnerability Data
LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. In versions 1.2.1 through 1.6.55, `png_set_tRNS` and `png_set_PLTE` each alias a heap-allocated buffer between `png_struct` and `png_info`, sharing a…
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single allocation across two structs with independent lifetimes. The `trans_alpha` aliasing has been present since at least libpng 1.0, and the `palette` aliasing since at least 1.2.1. Both affect all prior release lines `png_set_tRNS` sets `png_ptr->trans_alpha = info_ptr->trans_alpha` (256-byte buffer) and `png_set_PLTE` sets `info_ptr->palette = png_ptr->palette` (768-byte buffer). In both cases, calling `png_free_data` (with `PNG_FREE_TRNS` or `PNG_FREE_PLTE`) frees the buffer through `info_ptr` while the corresponding `png_ptr` pointer remains dangling. Subsequent row-transform functions dereference and, in some code paths, write to the freed memory. A second call to `png_set_tRNS` or `png_set_PLTE` has the same effect, because both functions call `png_free_data` internally before reallocating the `info_ptr` buffer. Version 1.6.56 fixes the issue.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 3 hardening rules · 3 OS baselines
V1.4.3
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation can discover use-after-free bugs through dynamic analysis or fuzzing.
Engineering principles can require memory-safe constructs or languages that structurally avoid introducing use-after-free.
Process isolation confines the blast radius of use-after-free memory corruption to a single execution domain.
Memory protection controls limit exploitation impact by blocking unauthorized code execution from dangling pointers.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly incorporate memory-safety tooling and reviews that prevent most use-after-free defects.
Vulnerability identification processes can discover use-after-free issues via scanning or analysis but do not prevent their introduction.
Routine patching removes known use-after-free instances after they have been introduced in released software.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development can detect use-after-free bugs before release.
Secure SDLC mandates memory-safety practices that reduce use-after-free defects.
Application security requirements can specify memory-management rules that mitigate use-after-free.
Secure architecture principles include memory-safety design choices that limit use-after-free exposure.
Secure coding standards directly prescribe avoidance of use-after-free patterns.
Change-management processes help ensure memory-safety fixes are deployed consistently.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (1 rule)
- V-248592 OL 8 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416
RHEL 8 (1 rule)
- V-230279 RHEL 8 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416
RHEL 9 (1 rule)
- V-257794 RHEL 9 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416