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fix(920240, 920400): don't rely on content-type header#4639

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EsadCetiner:fix-content-type-920240-920400
Jun 1, 2026
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fix(920240, 920400): don't rely on content-type header#4639
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EsadCetiner:fix-content-type-920240-920400

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@EsadCetiner

@EsadCetiner EsadCetiner commented May 17, 2026

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Proposed changes

Rules 920240 and 920400 relies on the Content Type header to perform urlencoding validation, and file size limits respectively. Some applications don't set content types correctly and will use something like text/plain.

The REQBODY_PROCESSOR variable contains the same information a Content Type would, and would support more exotic configurations where urlencoded data is sent with a text/plain content type. Assuming the end user switches on the correct body processor for text/plain and similar.

PR Checklist

  • I have read the CONTRIBUTING doc
  • I have added positive tests proving my fix/feature works as intended.
  • I have added negative tests that prove my fix/feature considers common cases that might end in false positives
  • In case you changed a regular expression, you are not adding a ReDOS for pcre. You can check this using regexploit
  • My test use the comment field to write the expected behavior
  • I have added documentation for the rule or change (when appropriate)

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AI Disclosure

N/A

For the reviewer

  • Positive and negative tests were added
  • Tests cover the intended fix/feature properly
  • No usage of dangerous constructs like ctl:requestBodyAccess=Off were used in the rule
  • In case a regular expression was changed, there is no ReDOS
  • Documentation is clear for the rule/change
  • If a contribution shows signs of unreviewed AI generation (e.g., plausible-but-broken regex, generic boilerplate comments, hallucinated SecLang directives), reviewers should ask about AI usage regardless of what was checked.

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📊 Quantitative test results for language: eng, year: 2023, size: 10K, paranoia level: 1:
🚀 Quantitative testing did not detect new false positives

@EsadCetiner EsadCetiner added release:fix backport:lts-4.25.1 PR that must be backported to LTS release 4.25.1 labels May 17, 2026

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@EsadCetiner I see the value of this, but does it make sense to add border case tests?

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@fzipi I think the existing test case is sufficient, we only support a handful of content-types so there's only so much we can do to thoroughly test. Any issues would likely be end-user configuration issues.

@fzipi
fzipi added this pull request to the merge queue Jun 1, 2026
Merged via the queue into coreruleset:main with commit 2f1afb7 Jun 1, 2026
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@EsadCetiner
EsadCetiner deleted the fix-content-type-920240-920400 branch June 1, 2026 11:20
@fzipi fzipi mentioned this pull request Jul 1, 2026
fzipi added a commit that referenced this pull request Jul 2, 2026
* fix: false positive with parameter name `.history` (#4614)

(cherry picked from commit 0885958)

* fix(942200): reduce false positives on payloads with comments (#4608)

* fix(942200): reduce false positives on payloads with comments

* add known fp test case

* improve test comments

* fix: wrong test

* add known fp test case

* fix typo

* fix typo

(cherry picked from commit 2c64b25)

* fix(unix): exclude `pg` command from pl-1 (#4613)

(cherry picked from commit 82195a4)

* fix(920100): drop HTTP/0.9 GET support from request line validation (#4621)

* fix(920100): drop HTTP/0.9 GET support from request line validation

remove the GET-without-protocol alternative from the regex assembly.
HTTP/0.9 is obsolete per RFC 9110 and the dedicated alternative was
the only one that did not require a protocol suffix in the request
line. GET requests with proper HTTP/1.x or HTTP/2 protocol versions
remain covered by the generic method alternative.

* Apply suggestions from code review

Co-authored-by: Max Leske <[email protected]>

---------

Co-authored-by: Max Leske <[email protected]>
(cherry picked from commit f8402a9)

* fix(920240, 920400): don't rely on content-type header (#4639)

(cherry picked from commit 2f1afb7)

* fix: remove exponential backtracking in 933160/933161 comment suffix (#4666)

* fix: remove exponential backtracking in 933160/933161 comment suffix

The suffix that skips whitespace and PHP comments between a function name
and the opening parenthesis used an ambiguous alternation where the
whitespace branch and the comment bodies both matched the same characters
under a `*` quantifier. On a backtracking engine a payload that never
reaches `(` backtracks exponentially.

De-ambiguate the alternation while keeping RE2 compatibility (no atomic
groups):
- block comments use the unrolled form instead of `/\*.*\*/`
- line comments (`#`, `//`) must terminate at a line break, because a line
  comment before `(` is only reachable across a newline; otherwise the `(`
  is inside the comment and there is no function call

Add positive tests for the comment/whitespace evasions (block, line with
newline, multi-line block, vertical tab, mixed) and negatives to 933161.

* docs: explain unrolled comment form in 933160/933161 .ra

* Update regex-assembly/933161.ra

Co-authored-by: Max Leske <[email protected]>

---------

Co-authored-by: Max Leske <[email protected]>
(cherry picked from commit c1df902)

* fix(941140): remove exponential backtracking in CSS url(javascript) detection (#4670)

* fix(941140): bound CSS declaration value to remove exponential backtracking

Move the inline pattern to regex-assembly/941140.ra and replace the free
'.+' in the declaration list with '[^;]+', removing the ambiguity that
caused exponential backtracking on backtracking engines (PCRE2/RE2 were
unaffected). Detection is unchanged (differential-tested).

* docs(941140): clarify whitespace handling and regression-test intent

Address review feedback on #4670:
- note that t:removeWhitespace strips whitespace before the regex runs, so
  the character classes intentionally do not account for it
- reword test_id 13 desc: it is a no-match canary for the unbounded-value
  shape (PCRE2 tames both old and new patterns), not a latency assertion

(cherry picked from commit fe59387)

* fix(933180): remove exponential backtracking in variable-function noise suffix (#4669)

* fix(933180): remove exponential backtracking in variable-function noise suffix

* fix(933180): require non-empty array/brace bodies in noise suffix

Address review on #4669: use + instead of * for the array-access and
curly-brace noise branches so empty [] / {} are not matched. This
restores the non-empty semantics of the original .+ patterns; the *
form had accidentally broadened them. Differential vs the original rule
shows zero true-positive loss; REQUEST-933 416/416 pass.

* test(933180): verify empty array/brace bodies are not matched

(cherry picked from commit 3828246)

* feat(crs-setup): add default actions for phases 3-5 (#4675)

(cherry picked from commit 09c1a11)

* fix: 4RI-250413 (#4672)

* fix: 4RI-250413

* fix: tests

* chore(formatting): auto fixes from pre-commit hooks

for more information, see https://pre-commit.ci

* fix: typo

* fix: tests

* apply code review suggestions

* apply code review suggestions

* chore(formatting): auto fixes from pre-commit hooks

for more information, see https://pre-commit.ci

* chore(942360): update regex with better format

Signed-off-by: Felipe Zipitria <[email protected]>

* fix(942362): add json. prefix support for JSON ARGS_NAMES

Rule 942362 uses a ^[\W\d]+ anchor that silently fails on libModSecurity3
because JSON payloads prepend json. (starting with j, a letter) to ARGS_NAMES.
Apply the same fix used in 942360/942361: ^(?:json\.)?[\W\d]+.

* Apply suggestions from code review

Co-authored-by: Max Leske <[email protected]>

* apply code review suggestions

* Update regex-assembly/942360.ra

Co-authored-by: Max Leske <[email protected]>

---------

Signed-off-by: Felipe Zipitria <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Felipe Zipitria <[email protected]>
Co-authored-by: Max Leske <[email protected]>
(cherry picked from commit 6e9ff3c)

* chore: release v4.25.1

* fix: correct indentation and action order in commented 900510 example

* docs: note libmodsecurity v3.0.16 requirement in CHANGES

* chore(tests): bump modsecurity-crs nginx image to libmodsecurity v3.0.16

* fix(901180): split XML attribute inspection gate to fix unused TX variable lint error

* fix: renumber duplicated test

Signed-off-by: Felipe Zipitria <[email protected]>

* fix: restore dropped json. prefix fixes and fix stale nginx CONNECT override

Cherry-picking PR #4672 (4RI-250413) took the LTS side wholesale for
rules/REQUEST-932-APPLICATION-ATTACK-RCE.conf and
rules/REQUEST-942-APPLICATION-ATTACK-SQLI.conf, then only regenerated
the rule IDs backed by a regex-assembly (.ra) file. Two hand-written
inline regexes with no .ra file (932171, 942361) were silently dropped
in that process and never got the `(?:json\.)?` ARGS_NAMES prefix fix,
so 942361-9 failed to detect the SQLi payload on nginx/libmodsecurity3.

Also updates the nginx-overrides.yaml entry for 920100 test 4: the
libmodsecurity v3.0.16 image bump also picked up nginx 1.30.3 (up from
1.28.2), which now rejects CONNECT with 405 instead of 400.

* docs: note ModSecurity v2 limitation for XML attribute opt-out in CHANGES

---------

Signed-off-by: Felipe Zipitria <[email protected]>
Co-authored-by: Esad Cetiner <[email protected]>
Co-authored-by: Max Leske <[email protected]>
Co-authored-by: Prateek saini <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
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