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No exploitation reportedFix available

CVE-2026-33416

No exploitation reported by the sources we read.

  • Published2026-03-26
  • Fixed in1.6.56
  • WeaknessCWE-416

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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 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.

Timeline

dates in UTC
  1. 2026-03-2617:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-33416?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-33416?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Libpng
BranchAffectedFixed in
1.x≥ 1.2.1, < 1.6.561.6.56

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • firefoxAlmaLinux:10all versions · fixed in 140.9.1-1.el10_1
  • firefoxAlmaLinux:9all versions · fixed in 140.9.1-1.el9_7.alma.1and 2 other packages
  • firefoxAlmaLinux:8all versions · fixed in 140.9.1-1.el8_10.alma.1and 1 other package
  • java-25-openjdkAlmaLinux:10all versions · fixed in 1:25.0.3.0.9-1.el10_2and 25 other packages
  • java-25-openjdkAlmaLinux:9all versions · fixed in 1:25.0.3.0.9-1.el9.alma.1and 25 other packages
  • libpngAlmaLinux:10all versions · fixed in 2:1.6.40-11.el10_2.1and 1 other package
  • libpngAlmaLinux:10all versions · fixed in 2:1.6.40-8.el10_1.4and 1 other package
  • libpngAlmaLinux:9all versions · fixed in 2:1.6.37-12.el9_7.4and 1 other package

6 more package ranges on OSV.dev

Full record on NVD

Fix

  1. Update Libpng to 1.6.56

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • NVDCVE recordread 2026-10-23
  • CISA-ADPSSVC decisionnone2026-03-31
  • OpenCVESSVC decisionnone—
  • CNACVSS 3.17.5read 2026-10-23
  • CNAweakness (CWE)CWE-416read 2026-10-23
  • FIRST EPSSEPSS score1.1 %2026-10-23
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Published
2026-03-26
Last Modified
2026-06-17
NVD status
Analyzed

Frequently asked questions

What is CVE-2026-33416?

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 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.

Is CVE-2026-33416 actively exploited?

Active exploitation of CVE-2026-33416 has not been confirmed. Its EPSS score was 1.1% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-33416?

CVE-2026-33416 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.

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