CVE-2026-52831

Nuclio: Unsanitized cron trigger event headers/body injected into CronJob shell command leads to persistent RCE

8.0 HighFix available

Nuclio is a "Serverless" framework for Real-Time Events and Data Processing. Prior to version 1.16.4, the Nuclio controller builds a curl invocation string for each cron trigger and stores it as the args of a Kubernetes CronJob container (/bin/sh, -c, <command>). Two fields in the trigger specification flow into this string without adequate sanitization: event.headers keys and event.body. This issue has been patched in version 1.16.4.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: High
Privileges needed: High
User interaction: None

What an attacker can affect

Confidentiality: High
Integrity: High
Availability: High

Exploit likelihood

0.53%Up 0.2 points since Sep 3, 2026

What each source reports

CVE List Score used 8.0

Nuclio: Unsanitized cron trigger event headers/body injected into CronJob shell command leads to persistent RCE

Record: CVE-2026-52831
CVSS 3.1: 8.0 HighCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
Weakness: CWE-78
Updated: 2026-11-02

EUVDEUVD-2026-70220 8.0

Record: EUVD-2026-70220
CVSS 3.1: 8.0 HighCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
Updated: 2026-11-02

GitHub AdvisoriesGHSA-v5px-423j-pf7p 10.0

Nuclio: Unsanitized cron trigger event headers/body injected into CronJob shell command leads to persistent RCE

Summary

Nuclio controller builds a curl invocation string for each cron trigger and stores it as the args of a Kubernetes CronJob container (/bin/sh, -c, <command>). Two fields in the trigger specification flow into this string without adequate sanitization:

event.headers keys — interpolated verbatim inside double-quoted --header arguments (lazy.go:2150); any key containing " breaks the quoting context.
event.body — processed with strconv.Quote, which escapes " and \ but not $(), allowing command substitution (lazy.go:2188).

Both paths were dynamically verified on Nuclio 1.15.27 (latest as of 2026-05-17).

CVSS 3.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H — 9.9 (Critical)
CWE: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)
Affected versions: Nuclio <= 1.15.27 (latest, dynamically verified)

Details

Root Cause

When a NuclioFunction with a cron trigger is reconciled by the controller, it calls generateCronTriggerCronJobSpec in pkg/platform/kube/functionres/lazy.go:2113. This function builds a shell command string by concatenating user-supplied values and passes it directly to /bin/sh -c.

Path-A — Header key injection (lazy.go:2146-2151)

// lazy.go:2146-2151
headersAsCurlArg := ""
for headerKey := range attributes.Event.Headers {
    headerValue := attributes.Event.GetHeaderString(headerKey)
    headersAsCurlArg = fmt.Sprintf("%s --header \"%s: %s\"",
        headersAsCurlArg, headerKey, headerValue)
    //                              ↑
    //                   headerKey is user-controlled; no escaping applied
}

headerKey is taken from event.headers in the trigger specification. Since it is interpolated directly inside a double-quoted shell argument, a key containing " terminates the quoting context. The remainder of the key is then interpreted as raw shell syntax.

Attack string for headerKey:

X-Inject"; ARBITRARY_COMMAND; echo "

Resulting shell command fragment:

--header "X-Inject"; ARBITRARY_COMMAND; echo ": value"

Path-B — Body command substitution (lazy.go:2173-2192)

// lazy.go:2188-2192
curlCommand = fmt.Sprintf("echo %s > %s && %s %s",
    strconv.Quote(eventBody),   // escapes " → \" and \ → \\, but NOT $()
    eventBodyFilePath,
    curlCommand,
    eventBodyCurlArg)

strconv.Quote wraps the string in double quotes and escapes " and \, but does not escape $, (, or ). A body value of $(CMD) becomes the Go string "$(CMD)", which the shell expands as command substitution when executing the /bin/sh -c string.

Attack string for event.body:

$(ARBITRARY_COMMAND)

Resulting shell command:

echo "$(ARBITRARY_COMMAND)" > /tmp/eventbody.out && curl ...

Execution sink (lazy.go:2212)

// lazy.go:2212
Args: []string{"/bin/sh", "-c", curlCommand}

The entire concatenated string — including any injected content — is executed by the shell.

Persistence mechanism

The CronJob created by the controller carries no ownerReferences linking it to the NuclioFunction. Kubernetes cascade deletion only applies to owned resources. If the controller crashes between function deletion and explicit CronJob deletion, the CronJob continues executing on its schedule indefinitely. The controller code itself acknowledges this at lazy.go:522:

// Delete function k8s CronJobs before the Deployment so they cannot spawn new
// CronJobs are not owned by the Deployment, so cascade does not remove them.

PoC

Environment Setup

The following steps reproduce the vulnerability in an isolated local environment.

Step 1 — Install prerequisites

# kind (Kubernetes-in-Docker)
curl -Lo /usr/local/bin/kind \
    https://kind.sigs.k8s.io/dl/v0.22.0/kind-linux-amd64
chmod +x /usr/local/bin/kind

# Helm
curl…

Record: GHSA-v5px-423j-pf7p
CVSS 3.1: 10.0 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Weakness: CWE-78
Updated: 2026-11-02

NVD 8.0

Record: CVE-2026-52831
CVSS 3.1: 8.0 HighCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
Weakness: CWE-78
Updated: 2026-11-02

OSV 8.0

Nuclio: Unsanitized cron trigger event headers/body injected into CronJob shell command leads to persistent RCE

Record: CVE-2026-52831
CVSS 3.1: 8.0 HighCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
Weakness: CWE-78
Updated: 2026-11-02

OSVGHSA-v5px-423j-pf7p 10.0

Nuclio: Unsanitized cron trigger event headers/body injected into CronJob shell command leads to persistent RCE

Summary

event.headers keys — interpolated verbatim inside double-quoted --header arguments (lazy.go:2150); any key containing " breaks the quoting context.
event.body — processed with strconv.Quote, which escapes " and \ but not $(), allowing command substitution (lazy.go:2188).

Both paths were dynamically verified on Nuclio 1.15.27 (latest as of 2026-05-17).

CVSS 3.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H — 9.9 (Critical)
CWE: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)
Affected versions: Nuclio <= 1.15.27 (latest, dynamically verified)

Details

Root Cause

Path-A — Header key injection (lazy.go:2146-2151)

// lazy.go:2146-2151
headersAsCurlArg := ""
for headerKey := range attributes.Event.Headers {
    headerValue := attributes.Event.GetHeaderString(headerKey)
    headersAsCurlArg = fmt.Sprintf("%s --header \"%s: %s\"",
        headersAsCurlArg, headerKey, headerValue)
    //                              ↑
    //                   headerKey is user-controlled; no escaping applied
}

Attack string for headerKey:

X-Inject"; ARBITRARY_COMMAND; echo "

Resulting shell command fragment:

--header "X-Inject"; ARBITRARY_COMMAND; echo ": value"

Path-B — Body command substitution (lazy.go:2173-2192)

// lazy.go:2188-2192
curlCommand = fmt.Sprintf("echo %s > %s && %s %s",
    strconv.Quote(eventBody),   // escapes " → \" and \ → \\, but NOT $()
    eventBodyFilePath,
    curlCommand,
    eventBodyCurlArg)

Attack string for event.body:

$(ARBITRARY_COMMAND)

Resulting shell command:

echo "$(ARBITRARY_COMMAND)" > /tmp/eventbody.out && curl ...

Execution sink (lazy.go:2212)

// lazy.go:2212
Args: []string{"/bin/sh", "-c", curlCommand}

The entire concatenated string — including any injected content — is executed by the shell.

Persistence mechanism

// Delete function k8s CronJobs before the Deployment so they cannot spawn new
// CronJobs are not owned by the Deployment, so cascade does not remove them.

PoC

Environment Setup

The following steps reproduce the vulnerability in an isolated local environment.

Step 1 — Install prerequisites

# kind (Kubernetes-in-Docker)
curl -Lo /usr/local/bin/kind \
    https://kind.sigs.k8s.io/dl/v0.22.0/kind-linux-amd64
chmod +x /usr/local/bin/kind

# Helm
curl…

Record: GHSA-v5px-423j-pf7p
CVSS 3.1: 10.0 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Weakness: CWE-78
Updated: 2026-11-02

OSVGO-2026-5946 No score

Nuclio: Unsanitized cron trigger event headers/body injected into CronJob shell command leads to persistent RCE in github.com/nuclio/nuclio

Nuclio: Unsanitized cron trigger event headers/body injected into CronJob shell command leads to persistent RCE in github.com/nuclio/nuclio

Record: GO-2026-5946
Updated: 2026-11-02

OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
GO-2026-5933 GHSA-3g4q-2f67-2gvh
GO-2026-5934 GHSA-59qp-cfj3-rp64
GO-2026-5935 GHSA-7856-g3gv-9wq8
GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
GO-2026-5942 CVE-2026-46600
GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
GO-2026-5969 GHSA-g936-7jqj-mwv8
GO-2026-5970 CVE-2026-56852
GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
GO-2026-5981 GHSA-mqxv-9rm6-w8qc
GO-2026-5982 GHSA-pqg7-v6wh-3pfp
GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
GO-2026-5985 GHSA-7rx3-5wx3-5v76
GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…

Record: openSUSE-SU-2026:21483-1
Updated: 2026-11-02

Affected products

nuclio

Affected packages

Affected packages
Package	Affected	Fixed
`github.com/nuclio/nuclio` Go	before 0.0.0-20260601075854-3356b86a8bfa	0.0.0-20260601075854-3356b86a8bfa
`govulncheck-vulndb` openSUSE:Leap 16.0 From an advisory covering 1734 CVEs	before 0.0.20260723T184607-160000.1.1	0.0.20260723T184607-160000.1.1

History

History
Recorded	Changed	Sources
Nov 6, 2026	affected, facts
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-52831 is a high vulnerability (CVSS 8.0) in Nuclio, published July 8, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.53%, the 45th percentile. Fixed in github.com/nuclio/nuclio 0.0.0-20260601075854-3356b86a8bfa.

References

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