ALPINE-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.
ALPINE-CVE-2026-33416
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:ALPINE-CVE-2026-33416
libpng
Source reference: /affected/0/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.6.56-r0
Source reference:
/affected/0/ranges - Prerequisites
- Not stated in this record
libpng
Source reference: /affected/1/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.6.56-r0
Source reference:
/affected/1/ranges - Prerequisites
- Not stated in this record
libpng
Source reference: /affected/2/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.6.56-r0
Source reference:
/affected/2/ranges - Prerequisites
- Not stated in this record
libpng
Source reference: /affected/3/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.6.56-r0
Source reference:
/affected/3/ranges - Prerequisites
- Not stated in this record
libpng
Source reference: /affected/4/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.6.56-r0
Source reference:
/affected/4/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "1.2.1"
},
{
"fixed": "1.6.56-r0"
}
]
}
],
"package": {
"name": "libpng",
"purl": "pkg:apk/alpine/libpng?arch=source",
"ecosystem": "Alpine:v3.20"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-33416.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "1.2.1"
},
{
"fixed": "1.6.56-r0"
}
]
}
],
"package": {
"name": "libpng",
"purl": "pkg:apk/alpine/libpng?arch=source",
"ecosystem": "Alpine:v3.21"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-33416.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "1.2.1"
},
{
"fixed": "1.6.56-r0"
}
]
}
],
"package": {
"name": "libpng",
"purl": "pkg:apk/alpine/libpng?arch=source",
"ecosystem": "Alpine:v3.22"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-33416.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "1.2.1"
},
{
"fixed": "1.6.56-r0"
}
]
}
],
"package": {
"name": "libpng",
"purl": "pkg:apk/alpine/libpng?arch=source",
"ecosystem": "Alpine:v3.23"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-33416.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "1.2.1"
},
{
"fixed": "1.6.56-r0"
}
]
}
],
"package": {
"name": "libpng",
"purl": "pkg:apk/alpine/libpng?arch=source",
"ecosystem": "Alpine:v3.24"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-33416.json"
},
"ecosystem_specific": {}
}
]Publisher severity
No explicit severity was provided.
- Event
- #54272 · Revision 1
- Added to Heist Feed
- Publisher date