CVE-2026-18568

Published Aug 3, 2026

Last updated a month ago

CVSS high 7.5

Overview

Description
XML::Sig versions from 0.29 before 0.72 for Perl allow signature verification bypass because verify returns true when every signature was skipped before any cryptographic check. verify in lib/XML/Sig.pm counts the `//dsig:Signature` elements into `$numsigs` and iterates over them, but two paths reach `next` before any digest or key check runs: a `SignedInfo/Reference/@URI` that resolves to no element while `$numsigs` is greater than 1, and, when `id_attr` is set, a reference that does not match the requested ID. The loop records nothing about what it checked, so when every signature takes one of those paths control reaches the unconditional `return 1` that ends verify. Two `Signature` elements whose Reference URI names an ID that no element carries is enough, as is one such element combined with `id_attr`. Any caller that passes untrusted XML to verify can receive a true return for a document in which no digest and no signature value was checked; a `cert` or `cert_text` trust anchor does not change this, because no key check runs. Versions up to 0.28 use an XML::XPath based verify that has no such skip and are not affected.
Source
9b29abf9-4ab0-4765-b253-1875cd9b441e
NVD status
Analyzed
Products
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Risk scores

CVSS 3.1

Type
Secondary
Base score
7.5
Impact score
3.6
Exploitability score
3.9
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Severity
HIGH

Weaknesses

9b29abf9-4ab0-4765-b253-1875cd9b441e
CWE-347

Social media

Hype score
Not currently trending

Configurations

Related CVEs

  1. XML::Sig versions before 0.71 for Perl allow signature wrapping via duplicate ID. _get_signed_xml() in lib/XML/Sig.pm, called from verify(), resolves the SignedInfo Reference/@URI to a node with the XPath expression "//*[@ID='$id']" and returns the first node of the resulting node set. A document in which two elements share that ID value is accepted: the digest and signature are checked against whichever element comes first in document order, and the duplicate is not detected. Such a document verifies successfully while an application that resolves the same ID independently can read the second, attacker supplied element; in a SAML2 context this places the contents of an Assertion under attacker control.•CVE-2026-9487
  2. XML::Sig versions before 0.71 for Perl allow XPath injection in ID lookup. verify() and _get_signed_xml() in lib/XML/Sig.pm build XPath expressions by concatenating the SignedInfo/Reference/@URI value read from the document being verified. The value is neither escaped nor checked against the NCName grammar that XML requires of an ID, so a URI containing a single quote closes the string literal in the generated expression and appends arbitrary XPath operators. A crafted URI can make the lookup match elements the reference does not name, or every element in the document, so which node is selected for digest verification is decided by the injected expression rather than by the reference.•CVE-2026-9390
  3. Archive::Tar versions before 3.10 for Perl allow memory exhaustion via attacker controlled entry size field in tar header. _read_tar() reads each entry's payload with $handle->read($$data, $block), where $block is derived from the entry's 12-byte size field in the tar header with no upper bound on that value. A crafted header declaring a multi-gigabyte size causes Perl to allocate a scalar of that size.•CVE-2026-9538
  4. Archive::Tar versions before 3.08 for Perl extract symlinks with attacker controlled targets outside the extraction directory. _make_special_file() passes the tar header's linkname to symlink() without validating it against absolute paths or .. segments. The secure-extract mode check that guards regular file extraction does not cover the symlink target. A subsequent open through the extracted name reads or writes the attacker chosen path.•CVE-2026-42496
  5. Archive::Tar versions before 3.08 for Perl extract hardlinks to attacker controlled paths outside the extraction directory. _make_special_file() passes the tar header's linkname to link() without validating it against absolute paths or .. segments, creating a hardlink that shares the victim file's inode. A subsequent write through the extracted name modifies the victim file, and the post-extraction chmod, chown, and utime block in _extract_file() (guarded only against symlinks via -l) applies the tar header's mode, owner, and timestamps to the shared inode during extraction alone.•CVE-2026-42497

References

Sources include official advisories and independent security research.