Endless recursion exists in xkbcomp/expr.c in xkbcommon and libxkbcommon before 0.8.1, which could be used by local attackers to crash xkbco

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

• canonical ubuntu linux14.04
• canonical ubuntu linux16.04
• canonical ubuntu linux18.04
• xkbcommon libxkbcommonbefore 0.8.1
• xkbcommon xkbcommonbefore 0.8.1

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Other highest-scoring records for the same primary product.

• CVE-2018-15857An invalid free in ExprAppendMultiKeysymList in xkbcomp/ast-build.c in xkbcommon before 0.8.1 could be used by local attackers to crash xkbc
  31Monitor
• CVE-2018-15864Unchecked NULL pointer usage in resolve_keysym in xkbcomp/parser.y in xkbcommon before 0.8.2 could be used by local attackers to crash (NULL
  22Monitor
• CVE-2018-15863Unchecked NULL pointer usage in ResolveStateAndPredicate in xkbcomp/compat.c in xkbcommon before 0.8.2 could be used by local attackers to c
  22Monitor
• CVE-2018-15862Unchecked NULL pointer usage in LookupModMask in xkbcomp/expr.c in xkbcommon before 0.8.2 could be used by local attackers to crash (NULL po
  22Monitor
• CVE-2018-15861Unchecked NULL pointer usage in ExprResolveLhs in xkbcomp/expr.c in xkbcommon before 0.8.2 could be used by local attackers to crash (NULL p
  22Monitor
• CVE-2018-15859Unchecked NULL pointer usage when parsing invalid atoms in ExprResolveLhs in xkbcomp/expr.c in xkbcommon before 0.8.2 could be used by local
  22Monitor

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

1function expand(node) {2  return node.children.map(expand);3}

1const MAX_DEPTH = 32;2function expand(node, depth = 0) {3  if (depth > MAX_DEPTH) throw new Error("too deep");4  return node.children.map((c) => expand(c, depth + 1));5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.