CVE-2026-73638: Out-of-bounds Read

Description

Imager versions from 0.45_02 before 1.035 for Perl read outside the EXIF block via unchecked start offsets in tiff_load_ifd. tiff_load_ifd() validates an IFD entry's data by checking that `entry->offset + entry->size` stays within the EXIF block, and never checks the start offset itself. Where that sum is not the real end of the data, the check passes with the entry starting outside the block. Through 1.032 `entry->offset` is a plain int, so on the usual two's-complement implementations an offset with the high bit set converts to negative and the sum can land back inside the block. From 1.033 the field is a size_t and the addition wraps only where size_t is 32 bits. The IFD's own start offset is checked the same way and wraps where unsigned long is 32 bits, which includes 64-bit Windows. Any caller of Imager->read() on an attacker-supplied image may receive EXIF tags holding bytes from outside the block, or crash the process.

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Weakness Type (CWE)

CWE-125 Out-of-bounds Read

References

Other References

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1144226 https://github.com/tonycoz/imager/commit/48ba8ac0749f89466b6e6681fb88cbdb51086ebd.patch https://github.com/tonycoz/imager/commit/6f1fd003a8e48c7e6e58b7019a04cc71bbfec2c3.patch https://github.com/tonycoz/imager/issues/568 https://github.com/tonycoz/imager/security/advisories/GHSA-j47j-8w8p-3mmc https://metacpan.org/release/TONYC/Imager-1.035/changes http://www.openwall.com/lists/oss-security/2026/09/17/5

Frequently Asked Questions

What is CVE-2026-73638? +

Imager versions from 0.45_02 before 1.035 for Perl read outside the EXIF block via unchecked start offsets in tiff_load_ifd. tiff_load_ifd() validates an IFD entry's data by checking that `entry->offset + entry->size` stays within the EXIF block, and never checks the start offset itself. Where that sum is not the real end of the data, the check passes with the entry starting outside the block. Through 1.032 `entry->offset` is a plain int, so on the usual two's-complement implementations an offset with the high bit set converts to negative and the sum can land back inside the block. From 1.033 the field is a size_t and the addition wraps only where size_t is 32 bits. The IFD's own start offset is checked the same way and wraps where unsigned long is 32 bits, which includes 64-bit Windows. Any caller of Imager->read() on an attacker-supplied image may receive EXIF tags holding bytes from outside the block, or crash the process.

How do I check if I'm vulnerable to CVE-2026-73638? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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