A flaw was found in Yelp due to an overly permissive Content Security Policy

yelp-xsl is the XSLT stylesheet package that drives Yelp, the GNOME desktop help viewer. This CVE is the CSP-policy half of the same family as CVE-2025-3155 — the stylesheets emit help-document HTML with a Content Security Policy permissive enough to allow inline scripting and external resource loads, so a crafted Mallard .page file can execute JavaScript inside the help viewer's WebKit context and reach file://, ghelp:///proc/self/cwd/... and similar URIs. The result is arbitrary file read in the context of the desktop user. Affected: yelp and yelp-xsl < 42.3 on GNOME-based distributions (Fedora, RHEL 8/9, Ubuntu 22.04/24.04, Debian 11/12 prior to backport).

Vendor scored this HIGH 7.1 with AV:L / S:C / C:H. The scope-changed confidentiality call is fair *for the affected component itself* — a help viewer that can read ~/.ssh/id_ed25519 is unambiguously out of bounds. But for a defender prioritizing 10,000 hosts, HIGH is overcalled: Yelp is a GNOME desktop component, not a server package; it requires a victim sitting at a Linux GUI to be tricked into opening a .page file (or visiting a site that abuses xdg-open/ghelp://). On a typical enterprise fleet this is a sub-1% population, no lateral movement, no RCE.

Why this verdict

• Local vector, desktop component: AV:L plus a GNOME-only package means the reachable population on a Windows-majority enterprise is a small minority of hosts.
• Role multiplier — workstation only: Yelp runs on (a) developer/admin Linux desktops and (b) end-user Linux desktops. It is not present on servers, hypervisors, IdPs, CAs, or any high-value role component. No deployment role exists where this bug yields fleet-scale, identity-scale, or supply-chain blast radius. Floor stays at MEDIUM.
• Friction — user interaction in practice: Despite UI:N in the vector, exploitation depends on a victim either opening a .page file or visiting a site that successfully invokes ghelp://. Modern browsers prompt on novel scheme handlers, neutering the drive-by path on most builds.
• Mitigations exist in the ecosystem: Flatpak'd Yelp is portal-sandboxed; SELinux/AppArmor confinement on RHEL/Ubuntu restricts some of the readable paths even pre-patch.

Why not higher?

Not HIGH because the blast radius is bounded to the desktop user's own files — no SYSTEM/root, no lateral movement primitive, and no high-value-role deployment of Yelp exists. KEV-absent and no observed exploitation. The vendor's S:C / C:H framing is technically correct for the component, but ignores fleet-level reachability.

Why not lower?

Not LOW because the primitive is arbitrary file read as the desktop user, which on a developer or admin workstation directly yields SSH keys, cloud credentials, and browser session tokens — a credible pivot input even if the bug itself doesn't pivot. A patched MEDIUM is correct; treating it as LOW would let admin Linux desktops linger unpatched.

1. Patch to yelp-xsl 42.3 / distro backport — This is a MEDIUM verdict — no noisgate mitigation SLA applies; ride the standard 365-day remediation window but pull it forward for any admin / developer Linux desktop in the next monthly maintenance cycle. Use dnf upgrade yelp yelp-xsl / apt-get install --only-upgrade yelp yelp-xsl.
2. Remove Yelp from server and kiosk images — If yelp ships in your gold image but the role never needs a help viewer (servers, build agents, CI runners), uninstall it: dnf remove yelp yelp-xsl or apt-get purge yelp yelp-xsl. Eliminates the attack surface entirely on those roles.
3. Unbind ghelp:// scheme handler on managed desktops — Until patched, edit /usr/share/applications/yelp.desktop to drop the x-scheme-handler/ghelp MimeType, or override per-user with xdg-mime default <noop>.desktop x-scheme-handler/ghelp. Kills the drive-by delivery path.
4. Enforce Flatpak Yelp where feasible — Flatpak'd Yelp uses xdg-document-portal and cannot freely read ~/.ssh/ — the primitive becomes far less useful. Roll Flatpak Yelp via Ansible/Salt to developer workstations as a hardening upgrade.
5. Audit egress for first-seen-domain HTTPS POSTs from desktops — Standard DLP / Zscaler / Netskope rules will catch the exfiltration leg even if the read primitive fires. Tune for credential-file-sized POSTs from non-browser processes.

Run on each Linux endpoint as any user (no root required) — e.g. bash check-cve-2026-13601.sh. Pushes via Ansible/Salt across the GNOME-desktop subset of your fleet. Exits 0 PATCHED, 1 VULNERABLE, 2 UNKNOWN (yelp not installed → not in scope).

#!/usr/bin/env bash
# noisgate check: CVE-2026-13601 — yelp-xsl permissive CSP
# Exit codes: 0=PATCHED  1=VULNERABLE  2=UNKNOWN/N-A
set -u
FIXED="42.3"

ver_ge() {
  # returns 0 if $1 >= $2 by dpkg/rpm semantics
  printf '%s\n%s\n' "$2" "$1" | sort -V -C
}

get_ver() {
  local pkg="$1"
  if command -v rpm >/dev/null 2>&1 && rpm -q "$pkg" >/dev/null 2>&1; then
    rpm -q --qf '%{VERSION}\n' "$pkg" | head -n1
    return
  fi
  if command -v dpkg-query >/dev/null 2>&1 && dpkg-query -W -f='${Version}\n' "$pkg" 2>/dev/null | grep -q .; then
    dpkg-query -W -f='${Version}\n' "$pkg" | sed 's/[-+~].*$//'
    return
  fi
  if command -v flatpak >/dev/null 2>&1 && flatpak info org.gnome.Yelp >/dev/null 2>&1; then
    flatpak info org.gnome.Yelp 2>/dev/null | awk -F': ' '/Version/{print $2; exit}'
    return
  fi
  echo ""
}

YELP_VER=$(get_ver yelp)
XSL_VER=$(get_ver yelp-xsl)

if [ -z "$YELP_VER" ] && [ -z "$XSL_VER" ]; then
  echo "UNKNOWN: yelp / yelp-xsl not installed — host not in scope"
  exit 2
fi

VULN=0
for pair in "yelp:$YELP_VER" "yelp-xsl:$XSL_VER"; do
  pkg="${pair%%:*}"; v="${pair##*:}"
  [ -z "$v" ] && continue
  if ver_ge "$v" "$FIXED"; then
    echo "OK: $pkg $v >= $FIXED"
  else
    echo "VULNERABLE: $pkg $v < $FIXED"
    VULN=1
  fi
done

[ "$VULN" -eq 1 ] && { echo "VULNERABLE"; exit 1; }
echo "PATCHED"
exit 0

Sources

1. Michael Catanzaro — CVE-2025-3155 yelp arbitrary file read (parent disclosure)
2. parrot409 PoC gist for the yelp-xsl exploit class
3. Red Hat advisory RHSA-2025:7569 (yelp / yelp-xsl)
4. Ubuntu USN-7447-1: Yelp vulnerability
5. Debian security tracker — yelp-xsl source package
6. Phoronix coverage of the yelp file-read class
7. Tenable plugin 237353 — RHEL 8 yelp / yelp-xsl
8. CISA Vulnerability Summary Bulletins (week of June 15, 2026)