HighPublic exploit

Use-after-free in libpng png_set_tRNS and png_set_PLTE

IdentifiersCVE-2026-33416CWE-416· Use After Free

CVE-2026-33416 is a use-after-free vulnerability in libpng affecting versions 1.2.1 through 1.6.55, with the underlying aliasing behavior for trans_alpha present since at least libpng 1.0. The flaw is in the low-level API functions png_set_tRNS and png_set_PLTE, which alias a single heap allocation between png_struct and png_info even though those structures have independent lifetimes. Specifically, png_set_tRNS assigns png_ptr->trans_alpha = info_ptr->trans_alpha for a 256-byte buffer, and png_set_PLTE assigns info_ptr->palette = png_ptr->palette for a 768-byte buffer. If png_free_data is later called with PNG_FREE_TRNS or PNG_FREE_PLTE, the buffer is freed through info_ptr while the corresponding pointer in png_ptr remains dangling. The same condition can also be triggered by a second call to png_set_tRNS or png_set_PLTE, because those functions internally call png_free_data before reallocating the info_ptr buffer. Subsequent row-transform operations may then dereference and, in some execution paths, write through the stale pointer, resulting in read-after-free and write-after-free conditions on heap memory.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can cause heap corruption, process crashes, and sensitive heap data exposure via read-after-free behavior. In code paths that write through the dangling pointer, the flaw can become a controlled write-after-free primitive. Supporting content states proof-of-concept exploitation demonstrated arbitrary code execution on some allocators with deterministic reuse behavior, such as glibc tcache. The issue is therefore potentially exploitable for arbitrary code execution in applications that process attacker-supplied PNG content through affected libpng code paths.

Mitigation

If you can’t patch tonight, do this now.

If immediate upgrade is not possible, reduce exposure by avoiding or restricting processing of untrusted PNG files in applications that invoke the affected libpng low-level API paths. Isolate image parsing in sandboxed or least-privileged processes and enable exploit mitigations such as ASLR and PIE where available, as the supporting content indicates exploitability is improved on systems with deterministic allocator reuse and weaker mitigations. No content-provided complete workaround short of patching is available for this CVE.

Remediation

Patch, then assume compromise.

Upgrade libpng to version 1.6.56 or later. The fix in 1.6.56 removes the unsafe shared-allocation aliasing by providing independently allocated copies for the affected pointers, preventing png_struct and png_info from sharing a single heap buffer with mismatched lifetimes.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

LibpngLibpngapplication

LibpngLibpng15application

MozillaThunderbirdapplication

Red HatLibpng12application

Red HatLibpng15application

Rocky LinuxRocky Linuxoperating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

30 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

30 SOURCESView more in app

cyber security newsNews

Apr 1, 2026

PNG Vulnerabilities Allow Attackers to Trigger Process Crashes, Leak Sensitive Information

A high-severity use-after-free vulnerability in libpng caused by pointer aliasing that can lead to heap corruption, sensitive information leakage, process crashes, and potentially arbitrary code execution via a crafted PNG file.

What this page doesn’t show

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity13