OESA-2026-1852 (CVE-2026-33416)
Vulnerability from osv_openeuler – Published: 2026-04-11 11:10 – Updated: 2026-08-06 11:10 – Source websiteThe libpng package contains libraries used by other programs for reading and writing PNG format files. The PNG format was designed as a replacement for GIF and, to a lesser extent, TIFF, with many improvements and extensions and lack of patent problems.
Security Fix(es):
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.(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 1.6.36 through 1.6.55, an out-of-bounds read and write exists in libpng's ARM/AArch64 Neon-optimized palette expansion path. When expanding 8-bit paletted rows to RGB or RGBA, the Neon loop processes a final partial chunk without verifying that enough input pixels remain. Because the implementation works backward from the end of the row, the final iteration dereferences pointers before the start of the row buffer (OOB read) and writes expanded pixel data to the same underflowed positions (OOB write). This is reachable via normal decoding of attacker-controlled PNG input if Neon is enabled. Version 1.6.56 fixes the issue.(CVE-2026-33636)
| URL | Type | |
|---|---|---|
{
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],
"database_specific": {
"severity": "High"
},
"details": "The libpng package contains libraries used by other programs for reading and writing PNG format files. The PNG format was designed as a replacement for GIF and, to a lesser extent, TIFF, with many improvements and extensions and lack of patent problems.\r\n\r\nSecurity Fix(es):\n\nLIBPNG 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-\u0026gt;trans_alpha = info_ptr-\u0026gt;trans_alpha` (256-byte buffer) and `png_set_PLTE` sets `info_ptr-\u0026gt;palette = png_ptr-\u0026gt;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.(CVE-2026-33416)\n\nLIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. In versions 1.6.36 through 1.6.55, an out-of-bounds read and write exists in libpng\u0026apos;s ARM/AArch64 Neon-optimized palette expansion path. When expanding 8-bit paletted rows to RGB or RGBA, the Neon loop processes a final partial chunk without verifying that enough input pixels remain. Because the implementation works backward from the end of the row, the final iteration dereferences pointers before the start of the row buffer (OOB read) and writes expanded pixel data to the same underflowed positions (OOB write). This is reachable via normal decoding of attacker-controlled PNG input if Neon is enabled. Version 1.6.56 fixes the issue.(CVE-2026-33636)",
"id": "OESA-2026-1852",
"modified": "2026-08-06T11:10:52Z",
"published": "2026-04-11T11:10:52Z",
"references": [
{
"type": "ADVISORY",
"url": "https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-1852"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33416"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33636"
}
],
"schema_version": "1.7.2",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H",
"type": "CVSS_V3"
}
],
"summary": "libpng security update",
"upstream": [
"CVE-2026-33416",
"CVE-2026-33636"
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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